Studying storms and getting information to the public is a 24/7 task this time
of year as Ivan is approaching the Gulf of Mexico.

The Tropical Prediction Center (TPC) is a component of the
National Centers for Environmental Prediction (NCEP) located at
Florida International University in Miami, Florida. The TPC mission is to
save lives, mitigate property loss, and improve economic efficiency by issuing
the best watches, warnings, forecasts and analyses of hazardous tropical
weather, and by increasing understanding of these hazards. Through international
agreement, the TPC has responsibility within the
World Meteorological Organization to generate and coordinate tropical
cyclone analysis and forecast products for twenty-four countries in the
Americas, Caribbean, and for the waters of the North Atlantic Ocean, Caribbean
Sea, Gulf of Mexico, and the eastern North Pacific Ocean. TPC products are
distributed through a close working relationship with the media and emergency
management communities.

The TPC collaborates with universities, government research
laboratories, international tropical weather centers, the private sector and
other National Weather Service components to maintain its leading edge in
tropical meteorology through coordinated operations, research, training and
forecast development techniques.

Chart A shows an approximate representation of coastal areas
under a hurricane warning (red), hurricane watch (pink), tropical storm warning
(blue) and tropical storm watch (yellow). The orange circle indicates the
current position of the center of the tropical cyclone. The black line and dots
show the National Hurricane Center (NHC) forecast track of the center at the
times indicated. The letter inside the dot indicates the NHC's forecast
intensity for that time.

NHC forecast tracks of the center can be in error; the average
track forecast errors in recent years were used to construct the areas of
uncertainty for the first 3 days (solid white area) and for days 4 and 5 (white
stippled area). The historical data indicate the entire 5-day path of the center
of the tropical cyclone will remain within the outer uncertainty area about
60-70% of the time. There is also uncertainty in the NHC intensity forecasts.
The intensity forecast chart and table below provide intensity forecast and
intensity forecast uncertainty information.

It is also important to realize tropical cyclones are not a
point. Their effects can span many hundreds of miles from the center. The area
experiencing hurricane force (one-minute average wind speeds of at least 74 mph)
and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can
extend well beyond the white areas shown enclosing the most likely track area of
the center. The distribution of hurricane and tropical storm force winds in this
tropical cyclone can be seen in the
Cumulative Wind Distribution graphic displayed below.

Chart B shows the probability, in percent, that the center
of the tropical cyclone will pass within 75 statute miles of a location during
the 72 hours beginning at the time indicated in the caption. The caption also
provides the name of the tropical cyclone and the advisory number from which the
probabilities were generated. Contour levels shown are 10%, 20%, 50% and 100%.

Chart C shows how the size of the storm has changed, and the areas potentially
affected so far by sustained winds of tropical storm force (in orange) and
hurricane force (in red). The display is based on the wind radii contained in
the set of Forecast/Advisories indicated at the top of the figure. Users are
reminded that the Forecast/Advisory wind radii represent the maximum possible
extent of a given wind speed within particular quadrants around the tropical
cyclone. As a result, not all locations falling within the orange or red swaths
will have experienced sustained tropical storm or hurricane force winds,
respectively.